It's official: Sebastian Vettel is a three-time world champion after Ferrari dropped the idea of challenging the result of the Brazilian Grand Prix.

The Italian team has written to the governing body the FIA requesting clarification as to whether Red Bull racer Vettel had illegally overtaken Jean-Eric Vergne's Toro Rosso during Sunday's race at Interlagos.

If that had been the case, Vettel would have incurred a 20 seconds penalty, demoting the German driver to eighth place and ensuring Ferari's Fernando Alonso would have won the drivers' title by one point.

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"The request for a clarification from the FIA, regarding Vettel's passing move on Vergne, came about through the need to shed light on the circumstances of the move, which came out on the Internet only a few days after the race," said a Ferrari statement on Friday.

"The letter to the FIA was in no way intended to undermine the legality of the race result.

"We received tens of thousands of queries relating to this matter from all over the world and it was incumbent on us to take the matter further, asking the Federation to look into an incident that could have cast a shadow over the championship in the eyes of all Formula 1 enthusiasts, not just Ferrari fans.

"Ferrari duly takes note of the reply sent by the FIA this morning and therefore considers the matter now closed."